1. Field of the Invention
The subject invention relates to a pen needle dispenser and, more particularly, to an apparatus that holds and dispenses sterile pen needles for medication delivery pens and that safely stores the needles after use.
2. Description of Related Art
Hypodermic syringes are used to deliver selected doses of medication to patients. The prior art hypodermic syringe includes a syringe barrel having opposed proximal and distal ends. A cylindrical chamber wall extends between the ends and defines a fluid receiving chamber. The proximal end of the prior art syringe barrel is substantially open and receives a plunger in sliding fluid tight engagement. The distal end of the prior art syringe barrel includes a passage communicating with the chamber. A needle cannula is mounted to the distal end of the prior art syringe barrel, such that the lumen of the needle cannula communicates with the passage and the chamber of the syringe barrel. Movement of the plunger in a proximal direction draws fluid through the lumen of the needle cannula and into the chamber. Movement of the plunger in a proximal-to-distal direction urges fluid from the chamber and through the lumen of the needle cannula.
Medication to be injected with the prior art hypodermic syringe often is stored in a vial having a pierceable elastomeric seal. Medication in the prior art vial is accessed by piercing the elastomeric seal with the needle cannula. A selected dose of the medication is drawn into the chamber of the syringe barrel by moving the plunger a selected distance in a proximal direction. The needle cannula is withdrawn from the vial, and the medication is injected into a patient by moving the plunger in a distal direction.
Some medication, such as insulin is self-administered. The typical diabetes patient will require injections of insulin several times during the course of the day. The required dose of insulin will vary from patient to patient, and for each patient may vary during the course of the day and from day to day. Each diabetes patient will establish a regimen that is appropriate for his or her own medical condition and for his or her lifestyle. The regimen typically includes some combination of a slow or medium acting insulin and a faster acting insulin. Each of these regimens may require the diabetes patient to periodically self-administer insulin in public locations, such as places of employment or restaurants. The required manipulation of the standard prior art hypodermic syringe and vial can be inconvenient and embarrassing in these public environments.
Medication delivery pens have been developed to facilitate the self-administration of medication. A prior art medication delivery pen is identified generally by the numeral 1 in FIG. 1. Pen 1 contains a cartridge with sufficient medication for several doses. The prior art cartridge has opposed proximal and distal ends. The distal end is closed by a pierceable and resealable rubber septum identified by the numeral 2 in FIG. 1. The proximal end receives a stopper in sliding fluid-tight engagement. The prior art cartridge is disposed in an elongate pen-like body 4 with a proximal end (not shown) and an opposed distal end 6. The proximal end of the pen body includes a plunger for selectively driving the stopper of the cartridge in the distal direction and a dose setting mechanism for determining the distance through which the plunger and stopper can move. Distal end 6 of pen body 4 includes an array of threads 8 for threaded engagement with a pen needle assembly 90. Pen needle assembly 90 includes a needle cannula 91 with opposed proximal and distal points 92 and 93 and a threaded mounting skirt 94 which surrounds the proximal tip 92. Mounting skirt 94 is threadedly engageable with threads 8 on distal end 6 of pen body 4. A safety shield 95 is releasably engaged over distal point 93 and portions of mounting skirt 94 to prevent accidental needle sticks.
A person who must periodically inject doses of medication will carry a medication delivery pen 1 and a supply of pen needle assemblies 90. Each pen needle assembly 90 has its needle cannula 91 safely and sterility sealed in its own shield 95, and is accessed immediately prior to administering a dose of medication. Pen needle assembly 90 then is mounted to distal end 6 of prior art pen 1. This mounting causes proximal point 92 of needle cannula 91 to pierce rubber septum 2 of the cartridge, to place needle cannula 91 in communication with the medication in pen 1. Pen 1 then is used to inject the selected dose of medication. After completing the injection, needle assembly 90 is separated from pen 1 and is discarded. Pen 1 may be used repeatedly in this manner until the medication is exhausted. Such prior art pens offer many conveniences and efficiencies. However, the storage of unused needles and the final disposal of used needles has presented problems. In particular, supplies of new needles often are loosely scattered in the bottom of purses or briefcases, and used needles are often disposed of unsafely.